How Prednisone Raises Blood Sugar
Prednisone, a synthetic glucocorticoid, mimics cortisol and boosts blood glucose by counteracting insulin and promoting glucose production. It binds to glucocorticoid receptors in the liver, muscle, and fat cells, triggering these effects within hours of dosing.[1]
Mechanism in the Liver
Prednisone induces gluconeogenesis, where the liver converts amino acids and glycerol into new glucose. It also ramps up glycogenolysis, breaking down stored glycogen into glucose for release into the bloodstream. These actions increase hepatic glucose output by 50-100% in some studies.[1][2]
Effects on Insulin and Fat Tissue
It impairs insulin signaling by inhibiting glucose uptake in muscle and fat cells, reducing GLUT4 transporter activity. In fat tissue, prednisone stimulates lipolysis, releasing free fatty acids that further elevate glucose via indirect pathways. This leads to insulin resistance, often spiking blood sugar 20-50 mg/dL or more in sensitive patients.[2][3]
Why Levels Stay High Long-Term
Chronic use sustains hyperglycemia because prednisone suppresses natural insulin production and alters gut hormone responses like GLP-1. Doses over 10 mg/day commonly cause this, with peaks 4-8 hours post-dose.[3]
Who Gets Hit Hardest
Diabetics or prediabetics see the biggest rises, but anyone on high/short-term bursts (e.g., 40-60 mg/day) risks it. Factors like obesity or infections amplify the effect.[1]
Managing the Spike
Monitor fasting glucose; taper doses when possible. Metformin or insulin adjustments help counteract it. Effects reverse 1-2 days after stopping short courses.[2][3]
Sources
[1] Endocrine Society - Glucocorticoid-Induced Hyperglycemia
[2] PubMed - Mechanisms of Corticosteroid-Induced Hyperglycemia
[3] UpToDate - Glucocorticoid-Induced Diabetes